CN114077067B - Vector light field generating device with arbitrary circular path change on polarization along poincare sphere - Google Patents

Abstract

A vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere, including a spatial light modulator, a first lens, an intensity controller, a spatial filter, a polarization controller, a second lens and a Ronchi grating , the intensity controller is composed of a half-wave plate and a polarizing beam splitter, the polarization controller is composed of a quarter-wave plate and a half-wave plate, and the linearly polarized light passes through the spatial light modulator and the first lens in sequence , a pair of intensity controllers, a spatial filter, a pair of polarization controllers, a second lens and a Ronchi grating to form a vector light field whose polarization changes along an arbitrary circular path on the Poincaré sphere. Compared with the existing technology, the optical path of the present invention is simple, and it does not require too many optical elements to generate a vector light field whose polarization changes along any circular path on the Poincaré sphere, and can realize various parameters of the device and the light field. precise corresponding control.

Description

Generation of a vector light field whose polarization changes along an arbitrary circular path on the Poincaré sphere device

Technical field

The invention relates to the field of optics, and in particular to a vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere.

Background technique

Vector light field refers to a light field with different polarization states at different positions on the same wave front at the same time. The Poincaré sphere is a model that represents polarization states. Each point on the sphere represents a different polarization state. Draw a circular path on the Poincaré sphere. If the polarization state on the wave surface of a type of light field changes along the spin direction, and the change is completely consistent with the polarization state change along the circular path on the Poincaré sphere, we call it It is a vector light field whose polarization changes along a circular path on the Poincaré sphere. This type of vector light field includes common radial polarization vector light fields, circular polarization vector light fields, hybrid polarization vector light fields and uniform elliptical polarization. rate vector light field, etc. The vector light field whose polarization changes along a circular path on the Poincaré sphere has been widely used in many fields such as quantum information, particle acceleration, single molecule imaging, optical micromachining, optical tweezers and optical micromanipulation.

How to generate various vector light fields flexibly and efficiently has always been a hot research topic in this field. Currently, vector light field generation methods can be divided into the following two categories: active generation methods and passive generation methods. The active generation method refers to the method of directly generating vector light fields through the laser resonator. Although this type of method has high generation efficiency, it lacks flexibility and can only generate a few specific vector light fields. Passive generation methods are divided into the following two categories: direct methods and indirect methods. Among them, the direct method in the passive generation method refers to the method of directly converting the scalar light field into a specific vector light field through the designed q-plate or metasurface material. In terms of flexibility, the direct method is improved compared to the active generation method, but it is still not flexible enough and reduces the generation efficiency. The indirect method in the passive generation method refers to the method of generating a vector light field through the coherent superposition of two light fields with orthogonal polarization states, also known as the interference method. The two coherent beams of light in the indirect method can be controlled by a spatial light modulator, providing extremely high flexibility.

The current indirect method based on the 4f system can be divided into the case of using one spatial light modulator and multiple spatial light modulators. For experimental solutions that use multiple spatial light modulators, they have the disadvantage of low efficiency in generating vector light fields due to the diffraction of the spatial light modulators. For the experimental plan using a single spatial light modulator, if one-dimensional grating modulation is loaded on the spatial light modulator, the disadvantage is that the types of vector light fields generated are greatly reduced, and only specific local linear polarization vector light fields can be generated. Hybrid polarization vector light field or uniform ellipsoidality vector light field; if two-dimensional grating modulation is loaded, the disadvantage is that the generation efficiency of the vector light field is greatly reduced.

Contents of the invention

In response to the above problems, the present invention proposes a device for generating a vector light field whose polarization changes along an arbitrary circular path on a Poincaré sphere. It only uses a spatial light modulator loaded with a one-dimensional grating and takes into account the generation of a vector light field. Compared with the case of using a single spatial light modulator and loading a one-dimensional grating, a richer variety of vector light fields can be generated. Compared with the case of using multiple spatial light modulators and loading a two-dimensional grating, it has Higher experiment generation efficiency.

The technical solution of the present invention is as follows:

A vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere, including a spatial light modulator, a first convex lens, an intensity controller, a spatial filter, a polarization controller, a second convex lens and a Ronchi grating , the spatial light modulator is located on the front focal plane of the first convex lens, the spatial filter is provided corresponding to the spatial light modulator, and is located between the first convex lens and the second convex lens, while It is also located at one focal length of the first convex lens, the Ronchi grating is located at the back focal plane of the second convex lens, and a pair of intensity controllers is located between the first convex lens and the spatial filter. between the pair of polarization controllers placed between the spatial filter and the second convex lens;

The linearly polarized light passes through the spatial light modulator, the first convex lens, the intensity controller, the spatial filter, the polarization controller, the second convex lens and the Ronchi grating in sequence, forming a vector whose polarization changes along any circular path on the Poincaré sphere. light field;

The expression of the vector light field that forms the polarization change along any circular path on the Poincaré sphere is:

in:

Among them: φ is the rotation coordinate of the light field wave surface;

m is the topological charge carried by the two-level orthogonal basis vectors of the vortex phase;

R determines the ellipsometry of the orthogonal basis polarization state;

θ determines the long axis direction of the orthogonal basis vector polarization state;

α determines the relative intensity ratio between orthogonal bases;

Controls the phase difference between orthogonal basis.

As described above, a vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere. The spatial light modulator includes a holographic grating. By changing the holographic grating on the light modulator, the light field polarization can be achieved. Control of period variation along a circular path on a Poincaré sphere and the origin of the circular path.

The transmittance of the holographic grating is:

Among them: y is the ordinate of the diffracted light in the spatial coordinate;

f ₀ is the spatial carrier frequency of the holographic grating;

φ is the rotation coordinate;

is the initial phase of the diffracted light;

m is the topological charge of diffracted light.

As described above, a vector light field generating device whose polarization changes along an arbitrary circular path on the Poincaré sphere. The holographic grating is a one-dimensional grating that can provide specific phase distribution for diffracted light of different orders. It is used in The one-dimensional grating modulation loaded on the spatial light modulator takes into account the type and generation efficiency of the vector light field generated.

As described above, a vector light field generating device whose polarization changes along an arbitrary circular path on the Poincaré sphere, the intensity controller includes a half-wave plate and a polarization beam splitter, and the half-wave plate is located on the polarization splitter. In front of the beam generator, a pair of the intensity controllers are arranged in parallel in front of the spatial filter. The intensity controllers can perform intensity control on the diffracted light before filtering, forming two stages of scalar light with any controllable light intensity ratio. .

As described above, a vector light field generating device whose polarization changes along an arbitrary circular path on the Poincaré sphere, the polarization controller includes a quarter wave plate and a half wave plate, and the quarter wave plate The wave plate is located in front of the half-wave plate, and a pair of polarization controllers are arranged after the spatial filter, which can perform polarization conversion on the filtered diffracted light, forming a two-stage scalar with any controllable polarization state. Light.

As described above, a vector light field generating device whose polarization changes along an arbitrary circular path on the Poincaré sphere, the Ranchi grating is arranged corresponding to the spatial filter, and the Ranchi grating can superimpose two orders of diffracted light , forming a vector light field whose polarization changes along an arbitrary circular path on the Poincaré sphere.

In the above-mentioned vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere, the first convex lens and the second convex lens are confocal.

The beneficial effects of the present invention are:

1. The invention discloses a vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere. Compared with the existing disclosed technology, the two-level light field is controlled by an intensity controller and a polarization controller. Intensity and polarization state, the two-level light field can be conveniently converted into a vector light field whose polarization changes along an arbitrary circular path on the Poincaré sphere using a small number of optical components.

2. The invention discloses a vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere. Compared with the existing technology, a single spatial light modulator and a one-dimensional grating are used to generate a vector light field. The efficiency is higher and the energy utilization rate is improved.

3. The invention discloses a vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere. Different vectors can be accurately adjusted through the spatial light modulator, intensity controller and polarization controller in the invention. The parameters in the light field correspond to the vector light field generated by any circular path on the simulated Poincaré sphere model, meeting the needs of the experiment.

Description of the drawings

The aspects and advantages of the present application will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating preferred embodiments only and are not to be construed as limiting the invention.

In the attached picture:

Figure 1 is a schematic diagram of a vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere according to the present invention;

Figure 2 shows the arbitrary circular path along the Poincaré sphere;

Figure 3 is a theoretical simulation and a vector light field of five kinds of uniform ellipsometry measured through experiments of the present invention;

Figure 4 is a theoretical simulation and a vector light field of five types of non-uniform ellipsometry measured through experiments of the present invention;

The components represented by each reference number in the figure are:

1. Spatial light modulator, 2. First convex lens, 3. Intensity controller, 301. First half-wave plate, 302. Second half-wave plate, 401. First polarization beam splitter, 402. Second polarization splitter Beamer, 5. Spatial filter, 6. Polarization controller, 601. First quarter-wave plate, 602. Second quarter-wave plate, 701. Third half-wave plate, 702. Fourth half-wave plate Wave plate, 8. Second convex lens, 9. Ronchi grating.

Detailed ways

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. It should be noted that these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. The present disclosure can be implemented in various forms and should not be used as described here. limited by the implementation.

The orientations "front and back", "left and right", etc. mentioned in the present invention are only used to express relative positional relationships and are not bound by any specific direction reference in practical applications.

Example

Referring to Figure 1, a vector light field generating device that changes along an arbitrary circular path on the Poincaré sphere includes a spatial light modulator 1, a first convex lens 2, an intensity controller 3, a spatial filter 5, and a polarization controller 6 , a second convex lens 8 and a Ronchi grating 9, the spatial light modulator 1 is located on the front focal plane of the first convex lens 2, the spatial filter 5 is provided corresponding to the spatial light modulator 1, and is located at the front focal plane of the first convex lens 2. Between the first convex lens 2 and the second convex lens 8, it is also located at one focal length of the first convex lens 2, and the Ronchi grating 9 is located at the back focal plane of the second convex lens 8, A pair of intensity controllers 3 is located between the first convex lens 2 and the spatial filter 5 , and a pair of polarization controllers 6 is located between the spatial filter 5 and the second convex lens 8 ;

The linearly polarized light passes through the spatial light modulator 1, the first convex lens 2, the intensity controller 3, the spatial filter 5, the polarization controller 6, the second convex lens 8 and the Ronchi grating 9 in sequence, forming a polarization along the Poincaré sphere. Vector light field with arbitrary circular path;

The expression of the vector light field that forms the polarization along any circular path on the Poincaré sphere is:

in:

Among them: φ is the rotation coordinate of the light field wave surface;

m is the topological charge carried by the two-level orthogonal basis vectors of the vortex phase;

R determines the ellipsometry of the orthogonal basis polarization state;

θ determines the long axis direction of the orthogonal basis vector polarization state;

α determines the relative intensity ratio between orthogonal bases;

Controls the phase difference between orthogonal basis.

In this embodiment, the spatial light modulator 1 includes a holographic grating. By changing the holographic grating on the spatial light modulator 1, the period and circular path of the light field polarization changing along the circular path on the Poincaré sphere can be achieved. Starting point control.

The transmittance of the holographic grating is:

Among them: y is the ordinate of the diffracted light in the spatial coordinate;

f ₀ is the spatial carrier frequency of the holographic grating;

φ is the rotation coordinate;

is the phase difference between orthogonal bases of diffracted light;

m is the topological charge carried by the two-level orthogonal basis vectors of the vortex phase.

In this embodiment, the holographic grating is a one-dimensional grating that can provide specific phase distribution for diffracted light of different orders. The ±1 order diffracted light respectively carries opposite vortex phases and is used in a spatial light modulator. One-dimensional grating modulation is loaded on 1. Compared with the existing technology, the type and generation efficiency of the vector light field can be taken into consideration.

In this embodiment, the intensity controller 3 includes a half-wave plate and a polarizing beam splitter, a first half-wave plate 301 and a first polarizing beam splitter 401, a second half-wave plate 302 and a second polarizing beam splitter. 402 forms a pair of intensity controllers, which are respectively set in front of the spatial filter 5 for intensity control of the diffracted light before filtering. The incident x-direction linearly polarized diffracted light passes through the first half-wave plate 301 or the second half-wave plate 301. The polarization long axis orientation behind the plate 302 can be controlled by adjusting the fast axis direction of the first half-wave plate 301 or the second half-wave plate 302. Since the first polarization beam splitter 401 or the second polarization beam splitter 402 can only transmit Linearly polarized light in the x-direction, so by controlling the polarization long axis orientation of the incident light, the intensity of the outgoing light can be controlled.

In this embodiment, the polarization controller 6 includes a quarter-wave plate and a half-wave plate. The quarter-wave plate is located in front of the half-wave plate. The first quarter-wave plate The wave plate 601 and the third half-wave plate 701, the second quarter-wave plate 602 and the fourth half-wave plate 702 form a pair of polarization modulators 6, which are respectively arranged after the spatial filter 5. It can polarize the filtered diffracted light to form scalar light with any controllable polarization state in two stages. Because the combination of a quarter-wave plate and a half-wave plate can convert a certain polarization state into any one. Therefore, by controlling the fast axis directions of these two wave plates, the emitted light can be controlled to be a scalar light field of arbitrary polarization.

In this embodiment, the Ronchi grating 9 is arranged corresponding to the spatial filter 5. The radio grating 9 can superimpose two levels of diffracted light to form a vector whose polarization changes along any circular path on the Poincaré sphere. light field.

In this embodiment, the spatial filter 5 is arranged corresponding to the spatial light modulator 1 and is arranged at one focal length to filter the diffracted light and filter out the high-frequency components.

In this embodiment, the first convex lens 2 is disposed between the spatial light modulator 1 and the spatial filter 5 , and the diffracted light is focused on the spatial filter 5 through the first convex lens 2 , the second convex lens 8 is disposed between the spatial filter 5 and the Ranch grating 9, and the two-order diffracted light is focused on the Ranch grating 9 through the second convex lens 8. Ronchi grating 9 can superimpose two orders of diffracted light to form a vector light field whose polarization changes along any circular path on the Poincaré sphere.

Furthermore, the first convex lens 2 and the second convex lens 8 are confocal.

Referring to Figure 2, the vector light field expression:

m controls the change period of the circular path;

R and θ control the position of the circular path;

α controls the radius of the circular path;

Controls the starting point of the change on the circular path.

In this embodiment, by changing the holographic grating on the spatial light modulator 1, it is possible to realize the change of the period m of the light field polarization along the circular path on the Poincaré sphere and the starting point of the circular path. control. By changing the fast axis direction of the first half-wave plate 301 or the second half-wave plate 302 in the intensity controller, the control of the circular path radius cosα of the light field polarization changing along the circular path on the Poincaré sphere can be achieved.

The Poincaré sphere can be realized by changing the fast axis direction of the first quarter-wave plate 601 or the second quarter-wave plate 602 and the third half-wave plate 701 or the fourth half-wave plate 702 in the polarization controller. Control of the position R and θ of the upper circular path.

Referring to Figures 3 and 4, the total intensity of each light field and the distribution of the three components of the Stokes parameter S ₁ , S ₂ and S ₃ are given. The maximum value 1 and the minimum value -1 of the Stokes parameter S ₁ correspond to the linear polarization state in the horizontal and vertical directions respectively, and the maximum value 1 and the minimum value -1 of the Stokes parameter S ₂ correspond to the ±45° direction respectively. In the linear polarization state, the maximum value 1 and the minimum value -1 of the Stokes parameter S ₃ correspond to the right-handed and left-handed circular polarization states respectively. Each light field can be used represented by these five parameters. The topological charge m of the following light fields is all 2, indicating a light field in which the polarization state changes twice along a circular path; θ is all π/3, so the two levels in the experiment have a phase difference of π/6. Therefore, the parameter m of the one-dimensional grating on the spatial light modulator is set to 2.

Referring to Figure 3, the theoretical simulation and experimental generation results of vector light fields with five polarization states changing along special circular paths (equator and latitude coils) on the Poincaré sphere are all vector light fields with uniform ellipsoidal polarization. , that is, the polarization ellipsometry at each position on the light field wave surface remains unchanged, and the long axis orientation changes along the rotational direction.

The generation conditions of the vector light field 1 require: the vector light field is obtained by superposing two levels of light fields with left and right circular polarization states respectively. It is required that the light intensity of the left circularly polarized light is greater than that of the right circularly polarized light. The first The angle between the positive direction of the fast axis of the half-wave plate 301 and the positive direction of the x-axis is 0, the angle between the positive direction of the fast axis of the second half-wave plate 302 and the positive direction of the x-axis is 1.465, and the angle between the positive direction of the first quarter-wave plate 302 and the positive direction of the x-axis is 1.465. The angle between the positive direction of the fast axis of the plate 601 and the positive direction of the x-axis is π/4, and the angle between the positive direction of the fast axis of the second quarter-wave plate 602 and the positive direction of the x-axis is 3π/4.

Referring to Figure 3, the polarization state at each position on the wave surface of the vector light field 1 is a left-handed elliptical polarization state with the same ellipticality. That is, the Stokes parameter _S3 of the entire light field is a negative number, and the length of the polarization state is The axis orientation rotates counterclockwise as the rotational coordinate increases.

The conditions for generating the vector light field 2 require that an initial phase of π/4 be written on the one-dimensional grating under the conditions for generating the vector light field 1 (which will not be described in detail here).

The polarization state at each position on the wave surface of the vector light field 2 is a left-handed elliptical polarization state with consistent ellipticality, that is, the Stokes parameter S ₃ of the light field is a negative number, and the long axis orientation of the polarization state changes with the rotation direction. Coordinates increase in counterclockwise rotation.

The conditions for generating the vector light field 3 are: the vector light field is obtained by superposing two levels of light fields with left and right circular polarization states respectively, and an initial phase of π/4 is written on the one-dimensional grating. The angle between the positive direction of the fast axis of the half-wave plate 301 and the positive direction of the x-axis is 0, the angle between the positive direction of the fast axis of the second half-wave plate 302 and the positive direction of the x-axis is 0, and the angle between the positive direction of the fast axis and the positive direction of the x-axis of the second half-wave plate 302 is 0. The angle between the positive direction of the fast axis of the plate 601 and the positive direction of the x-axis is π/4, and the angle between the positive direction of the fast axis of the second quarter-wave plate 602 and the positive direction of the x-axis is 3π/4.

Referring to Figure 3, the vector light field 3 is a local linear polarization vector field, and the polarization state at each position on the wave surface is a linear polarization state, that is, the Stokes parameter _S3 of the light field is 0. The long axis orientation of the polarization state rotates counterclockwise as the handedness coordinate increases.

The conditions for generating the vector light field 4 require: the vector light field is obtained by superposing two levels of light fields each in a right-left circular polarization state. The angle between the positive direction of the fast axis of the first half-wave plate 301 and the positive direction of the x-axis is 0, the angle between the positive direction of the fast axis of the second half-wave plate 302 and the positive direction of the x-axis is 0, and the angle between the positive direction of the fast axis and the positive direction of the x-axis of the first quarter-wave plate 601 is 3π/4 , the angle between the positive direction of the fast axis of the second quarter-wave plate 602 and the positive direction of the x-axis is π/4.

Referring to Figure 3, the vector light field 4 is a local linear polarization vector field, and the polarization state at each position on the wave surface is a linear polarization state, that is, the Stokes parameter _S3 of the light field is 0. The orientation of the long axis of the polarization state rotates clockwise as the handedness coordinate increases.

The conditions for generating the vector light field 5 require that under the conditions for generating the light field 4 (which will not be described in detail here), an initial phase of π/4 is then written on the one-dimensional grating.

Referring to Figure 3, the vector light field 5 is a local linear polarization vector field, and the polarization state at each position on the wave surface is a linear polarization state, that is, the Stokes parameter _S3 of the light field is 0. The orientation of the long axis of the polarization state rotates clockwise as the handedness coordinate increases.

Referring to Figure 4, the theoretical simulation and experimental generation results of vector light fields with five polarization states changing along circular paths (some non-special circular paths) on the Poincaré sphere are all polarization states with non-uniform ellipsometry. Vector light field.

The conditions for generating vector light field 1 in Figure 4 require: the vector light field is obtained by superposing two levels of light fields that are orthogonal to each other in right-handed circular polarization states, and the light intensity of right-handed circularly polarized light is required to be greater than that of left-handed circular polarization. For polarized light, the angle between the positive direction of the fast axis of the first half-wave plate 301 and the positive direction of the x-axis is 1.465, the angle between the positive direction of the fast axis of the second half-wave plate 302 and the positive direction of the x-axis is 0, and the angle between the positive direction of the fast axis and the positive direction of the x-axis of the second half-wave plate 302 is 0. The angle between the positive direction of the fast axis of a quarter-wave plate 601 and the positive direction of the x-axis is -1.183, and the angle between the positive direction of the fast axis and the positive direction of the x-axis of the second quarter-wave plate 602 is -1.183, so The angle between the positive direction of the fast axis of the third half-wave plate 701 and the positive direction of the x-axis is -0.733, and the angle between the positive direction of the fast axis and the positive direction of the x-axis of the fourth half-wave plate 702 is -0.45.

Referring to Figure 4, the polarization state at each position on the wave surface of the vector light field 1 is a right-handed elliptical polarization state, that is, the Stokes parameter S ₃ of the entire light field is a positive number, and the Stokes parameter S ₁ and S ₂ are also positive numbers. The ellipsometry and long-axis orientation of the polarization state of the vector light field both change along the handedness, and the long-axis orientation rotates clockwise as the handedness coordinate increases.

Conditions for generating vector light field 2: Under the conditions for generating vector light field 1 (which will not be described in detail here), an initial phase of π/4 is written on the one-dimensional grating.

Referring to Figure 4, the polarization state at each position on the wave surface of the vector light field 2 is a right-handed elliptical polarization state, that is, the Stokes parameter S ₃ of the light field is a positive number, and the Stokes parameters S ₁ and S ₂ is also a positive number. The ellipsometry and long-axis orientation of the polarization state of the vector light field both change along the handedness, and the long-axis orientation rotates clockwise as the handedness coordinate increases.

Generating conditions for vector light field 3: The vector light field is obtained by superposing two levels of linearly polarized light fields that are orthogonal to each other. An initial phase of π/4 is written on the one-dimensional grating. It is required that the first The angle between the positive direction of the fast axis of the half-wave plate 301 and the positive direction of the x-axis is 0, the angle between the positive direction of the fast axis of the second half-wave plate 302 and the positive direction of the x-axis is 0, and the angle between the positive direction of the fast axis and the positive direction of the x-axis of the second half-wave plate 302 is 0. The angle between the positive direction of the fast axis 601 and the positive direction of the x-axis is -1.047. The angle between the positive direction of the fast axis of the second quarter-wave plate 602 and the positive direction of the x-axis is -1.047. The angle between the positive direction of the fast axis of the second quarter-wave plate 602 and the positive direction of the x-axis is -1.047. The angle between the positive direction of the fast axis and the positive direction of the x-axis is -0.524, and the angle between the positive direction of the fourth half-wave plate 702 and the positive direction of the x-axis is -0.524.

Referring to Figure 4, vector light field 3 is a hybrid polarization vector field. It has both left and right circular polarization states, elliptical polarization states and linear polarization states on the wave surface. The ellipticality and long axis orientation of the polarization state of the vector light field are along the rotation direction. changes, in which the long axis orientation rotates counterclockwise as the rotational coordinate increases.

Generating conditions for the vector light field 4: The vector light field is obtained by superposing two levels of light fields that are orthogonal to each other in right-left circular polarization states. The positive direction of the fast axis of the first half-wave plate 301 and the positive direction of the x-axis The angle between the positive direction of the fast axis of the second half-wave plate 302 and the positive direction of the x-axis is 0, and the angle between the positive direction of the fast axis of the first quarter-wave plate 601 and the positive direction of the x-axis is -1.183, the angle between the positive direction of the fast axis of the second quarter-wave plate 602 and the positive direction of the x-axis is -1.183, and the angle between the positive direction of the fast axis of the third half-wave plate 701 and the positive direction of the x-axis is - 0.733, and the angle between the positive direction of the fast axis of the fourth half-wave plate 702 and the positive direction of the x-axis is -0.45.

Referring to Figure 4, the vector light field 4 wave surface has both left and right elliptical polarization states and linear polarization states. The ellipticity and long axis orientation of the polarization state of the vector light field change along the rotation direction, and the long axis orientation changes with the rotation direction. Coordinates increase with clockwise rotation.

The conditions for generating the vector light field 5 require that under the conditions for generating the light field 4 (which will not be described in detail here), an initial phase of π/6 is written on the one-dimensional grating.

Referring to Figure 4, the vector light field 5 wave surface has both left and right elliptical polarization states and linear polarization states. The ellipticity and long axis orientation of the polarization state of the vector light field change along the rotation direction, and the long axis orientation changes with the rotation direction. Coordinates increase with clockwise rotation.

The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can easily think of changes or modifications within the technical scope disclosed in the present invention. All additions, deletions, and substitutions shall be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (5)

1. A vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere, including a spatial light modulator (1), a first convex lens (2), an intensity controller (3), and a spatial filter ( 5), a polarization controller (6), a second convex lens (8) and a Ronchi grating (9), characterized in that the spatial light modulator (1) is located on the front focal plane of the first convex lens (2) , the spatial filter (5) is provided correspondingly to the spatial light modulator (1), and is located between the first convex lens (2) and the second convex lens (8), and is also located between the first convex lens (2) and the second convex lens (8). At one focal length of the first convex lens (2), the Ronchi grating (9) is located at the back focal plane of the second convex lens (8), and a pair of the intensity controllers (3) are located at the first Between the convex lens (2) and the spatial filter (5), a pair of the polarization controllers (6) is placed between the spatial filter (5) and the second convex lens (8); Linearly polarized light passes through the spatial light modulator (1), first convex lens (2), intensity controller (3), spatial filter (5), polarization controller (6), second convex lens (8) and Lang in sequence. Odd grating (9) forms a vector light field whose polarization changes along any circular path on the Poincaré sphere; The intensity controller (3) includes a half-wave plate and a polarizing beam splitter. The half-wave plate is arranged in front of the polarizing beam splitter. A pair of the intensity controllers (3) are arranged in parallel on the spatial filter. In front of the device (5), the intensity controller (3) can control the intensity of the diffracted light before filtering, forming two stages of scalar light with an arbitrary controllable light intensity ratio; The polarization controller (6) includes a quarter-wave plate and a half-wave plate, the quarter-wave plate is placed in front of the half-wave plate, and a pair of the polarization controllers (6) are arranged After the spatial filter (5), it can perform polarization conversion on the filtered diffracted light, forming two stages of scalar light with any controllable polarization state; The combination of a quarter-wave plate and a half-wave plate can convert a certain polarization state into any polarization state. By controlling the fast axis direction of the quarter-wave plate and half-wave plate, the outgoing light can be adjusted to any polarization. scalar light field; The expression of the vector light field that forms the polarization change along any circular path on the Poincaré sphere is: in: Among them: φ is the rotation coordinate of the light field wave surface; m is the topological charge carried by the two-level orthogonal basis vectors of the vortex phase; R determines the ellipsometry of the orthogonal basis polarization state; θ determines the long axis direction of the orthogonal basis vector polarization state; α determines the relative intensity ratio between orthogonal bases; Controls the phase difference between orthogonal basis. 2. A vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere according to claim 1, characterized in that the spatial light modulator (1) includes a holographic grating; The transmittance of the holographic grating is: Among them: y is the ordinate of the diffracted light in the spatial coordinate; f ₀ is the spatial carrier frequency of the holographic grating; φ is the rotation coordinate; is the phase difference between orthogonal bases of diffracted light; m is the topological charge carried by the two-level orthogonal basis vectors of the vortex phase. 3. A vector light field generating device whose polarization changes along an arbitrary circular path on the Poincaré sphere according to claim 2, characterized in that the holographic grating is a one-dimensional grating and can be of different levels. Diffracted light provides a specific phase distribution. 4. A vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere according to claim 1, characterized in that the Ronchi grating (9) and the spatial filter (5 ) corresponding to the setting, the Ronchi grating (9) can superimpose two orders of diffracted light to form a vector light field whose polarization changes along any circular path on the Poincaré sphere. 5. A vector light field generating device whose polarization changes along an arbitrary circular path on a Poincaré sphere according to claim 1, characterized in that the first convex lens (2) and the second convex lens (8) ) confocal.